I had my 2006 1.4 16v estate into the dealers last week (again) to look at a PAS problem which I had been having - excessive noise at startup. They partially resolved the noise by changing the fluid - which was full of crud. (That is a different story). They also did a revision of the car and "tweaked" some suspension items, etc... that I had mentioned which they didn't bother commenting on when I picked the car up.

Anyway, since the dealer visit the car has a strange vibration when I hit about 4500 rpm in 2nd or 3rd gear. I can feel it in the gear shift and steering wheel. It feels like a slightly unbalanced tyre, but seems directly related to engine rpm, not vehicle speed. It is quite noticeable when the car's full - motor under strain. I am worried that it could be something more serious in the drivetrain.

What could this be?

I forgot to mention that the motor sometimes pings (premature detonation) quite a bit under load as well. I put Extra or Supreme in all the time. Could this be related?